Anionic guest-dependent slow magnetic relaxation in Co(ii) tripodal iminopyridine complexes

Article abstract of DOI:10.1039/c9dt00739c

We report the syntheses and magnetic property characterizations of four mononuclear cobalt(ii) complex salts featuring a tripodal iminopyridine ligand with external anion receptor groups, [CoL^5-ONHtBu]X₂ (X = Cl (1), Br (2), I (3) and ClO₄ (4)). While all four salts exhibit anion binding through pendant amide moieties, only in the case of 1 is field-induced slow relaxation of magnetisation observed, whereas in the other salts this phenomenon is absent at the limits of our instrumentation. The effect of chloride inducing a seventh Co-N interaction and concomitant structural distortion is hypothesized as the origin of the observed dynamic magnetic properties observed in 1. Ab initio computational studies carried out on a 7-coordinate Co(ii) model species survey the complex interplay of coordination number and trigonal twisting on the sign and magnitude of the axial anisotropy parameter (D), and identify structural features whose distortions can trigger large switches in the sign and magnitude of magnetic anisotropy.

Full text of DOI:10.1039/c9dt00739c

View Article Online
View Journal
Dalton
Transactions
Accepted Manuscript
This article can be cited before page numbers have been issued, to do this please use: C. M. Klug, T. J.
Ozumerzifon, I. Bhowmick, B. N. Livesay, A. Rappe and M. Shores, Dalton Trans., 2019, DOI:
10.1039/C9DT00739C.
This is an Accepted Manuscript, which has been through the
Volume 45 Number
1 7 January 2016 Pages 1–398
Royal Society of Chemistry peer review process and has been
accepted for publication.
Dalton
Transactions
Accepted Manuscripts are published online shortly after
An international journal of inorganic chemistry
www.rsc.org/dalton
acceptance, before technical editing, formatting and proof reading.
Using this free service, authors can make their results available
to the community, in citable form, before we publish the edited
article. We will replace this Accepted Manuscript with the edited
and formatted Advance Article as soon as it is available.
You can find more information about Accepted Manuscripts in the
author guidelines.
Please note that technical editing may introduce minor changes
to the text and/or graphics, which may alter content. The journal’s
standard Terms & Conditions and the ethical guidelines, outlined
in our author and reviewer resource centre, still apply. In no
event shall the Royal Society of Chemistry be held responsible
for any errors or omissions in this Accepted Manuscript or any
consequences arising from the use of any information it contains.
ISSN 1477-9226
PAPER
Joseph T. Hupp, Omar K. Farha et al.
Efficient extraction of sulfate from water using
framework
a Zr-metal–organic
rsc.li/dalton

Please do not adjust margins
Page 1 of 10
Dalton Transactions
View Article Online
DOI: 10.1039/C9DT00739C
Journal Name
ARTICLE
Anionic Guest-Dependent Slow Magnetic Relaxation in Co(II)
Tripodal Iminopyridine Complexes
Received 00th
January 20xx,
Christina M. Klug,a,b Tarik J. Ozumerzifon,a,c Indrani Bhowmick,a,d Brooke N. Livesay,a Anthony K.
Rappé a and Matthew P. Shores a*
Accepted 00th January 20xx
DOI: 10.1039/x0xx00000x
www.rsc.org/
We report the syntheses and magnetic property characterizations of four mononuclear cobalt(II) complex salts featuring a
tripodal iminopyridine ligand with external anion receptor groups, [CoL5-ONHtBu]X2 (X = Cl (1), Br (2), I (3) and ClO4 (4)). While
all four salts exhibit anion binding through pendant amide moieties, only in the case of 1 is field-induced slow relaxation of
magnetisation observed, whereas in the other salts this phenomenon is absent at the limits of our instrumentation. The
effect of chloride inducing a seventh Co-N interaction and concomitant structural distortion is hypothesized as the origin
of the observed dynamic magnetic properties observed in 1. Ab initio computational studies carried out on a 7-coordinate
Co(II) model species survey the complex interplay of coordination number and trigonal twisting on the sign and magnitude
of the axial anisotropy parameter (D), and identify structural features whose distortions can trigger large switches in the
sign and magnitude of magnetic anisotropy.
Fe(II) complexes with tren-capped iminopyridine ligands,
where anion-binding groups are installed at the pyridine 5-
position and steric bulk is absent at the 6-position (Figure 1,
right), are low spin (S = 0) irrespective of guest presence.16
Nevertheless, the complexes show chloride binding in polar
(acetonitrile) solution.
Introduction
Efforts to control the switching of magnetic properties at
the molecular level have advanced the feasibility of devices for
nanoscale data storage, actuators and sensors. Magnetic
bistability exhibited by single-molecule magnets (SMMs) may
also be exploited in molecular switching applications. For
instance, reports have shown first row transition metal
complexes that can switch between spin crossover and SMM
properties.1–5 Other cases have shown magnetic relaxation
profiles in SMMs can be modulated by intermolecular
interactions. This phenomenon is sensitive to guest and/or
solvent inclusion in both molecular systems6–10 and extended
structures, such as metal-organic framework materials.11,12
Herein, we describe a complex architecture where anionic
guest binding far from the metal centre nevertheless imparts a
strong effect on magnetic relaxation dynamics.
To further develop the field of guest-dependent magnetic
switching in molecular species, we have focused on complexes
with tripodal iminopyridine ligands that contain anion-
receptors. Related tris(2-aminoethylamine) (tren)-derived
species have been shown to possess sterically-tuned spin
crossover properties;13–15 further, the hexa- or heptadentate
coordination environment might be expected to promote
complex stability in solution. Specifically, we have found that
3+
+
N
N
N
N
N
N
N
N
N
N
N
CoII
N
FeII
N
R
O
H
O
O
R
O
NR
R
O
N
R
Cl
Na
O
H
H
O
N
R
H
H
R = NHtBu
R = tBu
Figure 1. Differences in metal and guest binding pockets between previously
reported tach- and tren-based M(II) podands. Gray and blue circles represent
metal and guest binding pockets, respectively. The tach-containing pocket (left)
enforces hexacoordinate geometries, while the tren-based ligand (right) allows
for hexa- and hepta-coordinate geometries.
In contrast, related ligand sets bound to Co(II) yield high
spin (S
= 3/2) ground states. These ions have been
incorporated into a growing number of mono- and polynuclear
SMM complexes,17–19 as the intrinsically large spin-orbit
coupling value for Co(II) gives rise to significant zero-field
splitting (ZFS).20–22 Ligand distortion of the first coordination
sphere of the Co(II) ion has large impacts on axial (D) and
rhombic (E) anisotropy parameters.9,22,23 In a related example,
our recently reported cis-,cis-1,3,5-triaminocyclohexane (tach)-
capped Co(II) tripodal complex (Figure 1, left) displays unusual
a. Department of Chemistry, Colorado State University, Fort Collins, CO 80523, USA.
b. Current affiliation: Pacific Northwest National Laboratory.
c. Current affiliation: Isola USA Corporation, Chandler, AZ 85224, United States
d. Current affiliation: Colorado State University, Pueblo
Electronic Supplementary Information (ESI) available: details of magnetic and
computational studies. Crystallographic data for 1-4 submitted as CCDC 1030387 –
1030390. DOI: 10.1039/x0xx00000x
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 1
Please do not adjust margins

Please do not adjust margins
Dalton Transactions
Page 2 of 10
ARTICLE
cationic guest association and slow magnetic relaxation.24
Journal Name
For salts 1-4, one anion is encapsulated within the trigonal
View Article Online
DOI: 10.1039/C9DT00739C
However, we also found that the inherent rigidity of the tach- pocket formed by the three tert-butylamide functionalities of
based scaffold renders the complex coordination environment the ligand. The area of the triangular pocket formed by the
around cobalt insensitive to guest association.
carbon atoms of the amide carbonyl in the halide series ranges
Therefore, to modulate the magnetic properties of Co(II) from 19.03(1) Å2 in 1 to 21.89(6) Å2 in 3 (Table S2), highlighting
podand complexes via guest inclusion, we have implemented a the increased flexibility of the tren capping ligand. In
more flexible ligand cap derived from tren (Figure 1). In the comparison, the same areas measured for the more rigid tach
present work, the syntheses and magnetic characterizations of analogues vary only between 13.40(3) and 14.38(6) Å2.24
a series of Co(II) complex salts are reported, where the results
Table 1. Selected crystallographic parameters.
suggest turn-on magnetic relaxation as a function of guest
[CoL5-OOMe
[CoCl4]a
2.6262(2)
2.079(1)
2.228(1)
2.068(2)
1.27
]
anion. To tease apart the key structural factor that drive the
magnetic switching, we also report the results of an in-depth
computational investigation of the effects of introducing a
seventh ligand into a face-capped octahedral system.
1
2
3
4
Co-Nbridge (Å)
Co-Nim (Å)b
2.574(3)
2.120(6)
2.262(3)
2.099(2)
1.18
2.592(4)
2.106(6)
2.253(3)
2.092(3)
1.23
2.633(6)
2.105(3)
2.258(3)
2.068(4)
1.30
2.706(2)
2.100(5)
2.246(5)
2.075(2)
1.49
Co-Npy (Å)b
im-py dist (Å)c
SHAPE value
Results and Discussion
a
b
Structure where methyl ester replaces the amide group; from ref 21. Average
c
Complex salt syntheses and anion-binding properties
distance for 4. Distance between the planes defined by the imine and pyridine
nitrogen atoms, respectively. d Trigonal twisting angle of 0° gives a trigonal prism,
while 60° gives an octahedron.
The compounds [CoL5–ONHtBu]X2 (where X = Cl (1), Br (2), I
(3), or ClO4 (4)) are synthesized by combining the respective
CoX2 starting material and tripodal iminopyridine L5–ONHtBu in
methanol. Diffusion of diethyl ether into concentrated crude
reaction mixtures (as methanolic solutions) readily affords
diffraction-quality orange crystals of the four salts. The halide
Given the isotropy of the halide guests, it is not surprising
that the interactions with the arms are identical, which leads
to three-fold symmetry of the complex cation. In comparison,
the asymmetry of the bound perchlorate in 4 makes these
interactions distinct: one oxygen of the perchlorate engages in
a bifurcated hydrogen bond with two amides while another
oxygen engages in a hydrogen bond to the third arm of the
ligand; the third oxygen atom in the “trigonal” pocket does not
interact with amide hydrogen atoms. In fact, the structure of 4
is distinct from 1-3 in that the three amide N-H groups are not
oriented toward the molecular three-fold axis (Figure 2, right).
The packing of complexes 1-3 results in the formation of
channels within the structure, which contain severely
disordered solvent molecules and the remaining charge
balancing anion. The intermolecular Co···Co distances range
from 8.003(8) Å in 4 to 9.480(9) Å in 3. For complexes 1-3, the
packing and longer intermolecular distances effectively isolate
the complexes from each other. However, in 4, short
intermolecular contacts are present between the perchlorate
bound within the trigonal pocket and the tren ethylene
backbone of an adjacent cation (Figure S2), forming
supramolecular chains. These interactions may provide
pathways for intermolecular magnetic exchange.
3
salts 1-3 crystallize in the trigonal space group P , whereas the
1
perchlorate salt 4 crystallizes in P . The first coordination
spheres of the metal centres show the expected N6
environment in a distorted octahedron (Figures 2 and S1),
capped on one face by the bridging nitrogen atom from the
tren backbone (Nbridge, Table 1) providing a pseudo-
heptacoordination environment around the cobalt(II) centre.
As shown in Table 1, the Co–Nimine bonds (average 2.108(3) Å)
in 1-4 are shorter than the Co–Npyridine bonds (average 2.255(1)
Å), consistent with previously reported iminopyridine-based
first row transition metal complexes.13,25,26 The degree of
distortion from an ideal capped octahedron was measured
using the continuous shape measurement analysis using the
SHAPE 2.0 software.27,28 The afforded values were found to be
between 1.18-1.49, suggestive of
a distorted capped
octahedron coordination geometry for all four complexes.
Whereas the geometry of the tach-containing analogue of
1-4 is insensitive to guest inclusion, we may expect more
guest-induced ligand distortion from the larger tren capping
group. Compounds 1-4 crystallized with an anion contained in
the tris(amide) pocket. Notwithstanding, structural
comparison to the previously reported25 ester-containing
analogue, which does not contain a guest in the trigonal
pocket, reveals the anticipated geometric flexibility (Table 1).
Interestingly, the presence or absence of guest anions does
not significantly change the trigonal twisting in the Co(II)
complexes. For the ester-containing analogue, the interaction
between Co and the seventh ligand (Co-Nbridge distance) is in
the middle of the range provided by compounds 1-4.
Figure 2. Crystal structures of the complex cations of 1 (left) and 4 (right)
depicted with 40% thermal ellipsoids. Orange, green, red, blue, gray and white
ellipsoids represent Co, Cl, O, N, C and H atoms, respectively. Hydrogen atoms
not involved in hydrogen bonding and unbound anions have been omitted for
clarity. The structure for 1 resides on a three-fold rotation site, while the
complex for 4 sits on a general position.
2 | J. Name., 2012, 00, 1-3
This journal is © The Royal Society of Chemistry 20xx
Please do not adjust margins

Page 3 of 10
Dalton Transactions
Please do not adjust margins
Journal Name
ARTICLE
Additionally, the imine-pyridine interplane distance is as short interactions has been reported for Co(VIIie)-wcAorntictlae iOnnilninge
or shorter than all of the amide-containing structures, compounds previously.30
DOI: 10.1039/C9DT00739C
signalling elongation upon anion binding. These distance
We note that the reduced magnetisation data obtained for
changes highlight the flexibility of the tren backbone to compounds 1-4 (Figure S14) also support the assignment of S =
respond to guest species.
3/2 ground states for all complex salts. These data were fit in
tandem with susceptibility data using PHI.29 The results are
consistent with the magnetic behaviour of the perchlorate salt
Complex salt magnetic properties
Temperature dependent magnetic susceptibility data for 1- of the ester-containing analogue,25 and indicate that the
4 (Figures 3 and S10-S13) indicate that all species are high spin geometric changes upon interaction with anions are too small
(S = 3/2) over the temperatures probed. At 300 K, the χMT to impact spin state properties.
values are 2.96, 2.84, 3.02 and 2.92 cm3 K mol–1 for
Table 2. Comparison of magnetic parameters obtained from fits to magnetic
compounds 1-4, respectively; larger than the expected spin-
susceptibility data (PHI)29 and CASCI computations.
only value (1.875 cm3
K
mol–1), but consistent with
Experiment a
Computation
observations for many Co(II) complexes.23 The χMT products of
all species decrease gradually upon cooling from 300 to 50 K.
For the halide-bound salts, significant downturns below 50 K
are observed; these are attributed to magnetic anisotropy
and/or intermolecular antiferromagnetic interactions. For the
perchlorate salt 4, the χMT value increases between 50 K and 8
K, to 2.49 cm3 K mol–1, before dropping off like the others,
Salt
gx, gy, gz
|E/D|
gx, gy, gz
D b
|E/D|
D b
1
2
3
4
2.31, 2.39,
2.10
1.87, 2.56,
2.39
2.14, 2.25,
2.32
3.55, 0.75,
1.04
9.20
0.002
2.18, 2.30,
2.30
2.18, 2.30,
2.30
2.17, 2.31,
2.32
2.16, 2.34,
2.34
9.8
0.03
2.19
3.61
4.21
<0.001
0.399
0.060
5.9
0.010
0.006
0.002
12.4
15.9
suggesting
additional
intermolecular
ferromagnetic
interactions. Compounds 1-4 show χMT values of 1.52, 2.03
1.59, and 2.04 cm3 K mol–1 at 2 K, respectively, consistent with
anisotropic quartet ground states.
a
Although fits to reduced magnetization do not reliably give signs for D, the
b
experimental and computational signs agree here; see Table S4 for details.
values given in cm-1.
D
Anion dependence in SMM properties
While the extracted anisotropy parameters are modest
relative to many mononuclear Co(II) SMMs, we observe an
interesting anion dependence in this series. Chloride salt 1 has
a (relatively) larger axial anisotropy D value than the other
salts, and axiality (minimization of E/D) is strongest in the
chloride and bromide salts. Testing compounds 1-4 for SMM
properties, we note that none of the salts display out-of-phase
susceptibility (χʺ) responses under zero applied dc field at 1.8
K. Upon application of an external dc field, however, chloride
salt 1 exhibits slow relaxation of magnetisation (Figure 4),
where the χʺ signal is maximized at 2500 Oe (Figures S16-S17).
Figure 3. Variable temperature dc magnetic susceptibility data for 1-4 collected
between 1.8 and 300 K at an applied field of 1000 Oe. The fit lines were
determined using PHI29
, with the parameters obtained found in Table 2.
Individual figures for 1-4 can be found in the SI.
Fitting the magnetic susceptibility data to standard spin
Hamiltonians with PHI29 supports anisotropic quartet ground
states for all four salts (Tables 2 and S3). We note that the sign
of the axial anisotropy parameter is not reliably determined
from susceptibility data, but the positive signs are consistent
with fits to the reduced magnetization data. A small positive
mean field contribution is included in the fits of 1 and 4,
suggesting weak anti- and ferromagnetic interactions between
complexes (zJ
= 4
-0.099 and 0.028 cm-1, for 1 and
respectively), possibly arising from short intermolecular
contacts noted in the structural studies; ferromagnetic
intermolecular coupling mediated by hydrogen-bonding
Figure 4. Frequency dependence of the out-of-phase susceptibility for 1-4 at
listed applied dc fields. Data were collected at 1.9 K using a 4 Oe oscillating field.
Lines are guides to the eye.
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 3
Please do not adjust margins

Please do not adjust margins
Dalton Transactions
Page 4 of 10
ARTICLE
Journal Name
The bromide salt 2 displays a negligible out-of-phase response chloride (184 pm) to bromide (196 pm) to iodiVdieew A(2rti2cl0e Opnmline)
DOI: 10.1039/C9DT00739C
even with the application of a dc field up to 5000 Oe (Figure enlarges the ligand pocket, distorting the cobalt coordination
S18). Meanwhile, the iodide (3) and perchlorate (4) salts show sphere. It has been shown that altering the geometry around a
slight increases in the out-of-phase magnetic susceptibilities cobalt(II) centre can alter relaxation properties,20,22 so this may
under applied dc field at higher frequencies (Figures S19-S20), enable pathways for fast magnetic relaxation for 2 – 4, which
but do not produce maximum responses with the frequency are inaccessible for 1.
limits of our instrument. Further, the perchlorate salt of the
Focusing on the halide salts, two observable
analogous ester-containing complex also does not exhibit slow crystallographic trends are the compression of the N-donor
relaxation at the limits of our measurement (Figure S23, Hdc
=
]
atom planes along the 3-fold trigonal axis (Table 1), and an
increase in Co–Nbridge distance from the chloride to bromide to
2500 Oe). The local coordination geometry of the [CoL5-OOMe
complex in the tetrachlorocobaltate salt25 is most comparable iodide salt. The ester-containing analogue, the closest proxy
to the anion-bound species 3 and 4, which also do not show available for non-binding by anion, adds to the former trend
slow relaxation even under applied dc fields.31
with an even shorter imine-pyridine interplane distance. These
The temperature and frequency dependencies of the ac structural trends coincide with a decrease in experimentally-
magnetic susceptibility were studied for 1 under an applied dc derived axiality (E/D) as halide size increases. Comparison to
field of 2500 Oe for a range of temperatures (1.8–4.6 K). other C3-symmetric Fe(II) and Co(II) species employing tripodal
Maxima in the χʺ data are observable between 1.8 and 3.0 K ligands capped by a nitrogen atom show that an increase in
(Figure 5), and can be fit to an Orbach-only relaxation process, M–Nbridge distance leads to a decrease in the magnitude of D,
where τ-1 = τ0-1exp(-Ueff/kT). This treatment gives τ0
=
with concomitant effects on SMM properties.38–40 In our
1.33×10–6 s and Ueff = 9.2 cm-1 (Figure S21). While most system, chloride salt 1 has the shortest Co–Nbridge distance and
seven-coordinate
bipyramidal, the thermal barrier (Ueff
Co(II)
SMMs
are
pentagonal is the only compound that shows field-induced slow magnetic
and pre- relaxation.
)
exponential constant (τ0) are in agreement with those
previously reported.32–37
Computational exploration of ligand distortion effects on Co(II)
magnetic anisotropy
Whereas the experimental data suggest magnetic property
control via steric interactions, especially in terms of axiality
(E/D), computational results do not provide the same
correlation. Computations were carried out at several levels of
theory on systems closely related to the experimentally
determined structures, and results are summarized in Tables
S5-S9. An important caveat is that anions not located in the
tris(amide) binding pockets are severely disordered in the
halide-containing structures, so their placement along the 3-
fold rotational axis for computations offers consistency and
convenience, but also removes rhombic anisotropy by
symmetry arguments. Notwithstanding, and not surprisingly,
the more resource-intensive NEVPT241–44 or CASCI45
computations give better numerical agreement with measured
D values, while density functional (B3LYP)46 calculations give
|D| values about half of what are measured. However, the
trends are similar with all sets of computations. For example,
in both cases, the Br-containing salt is expected to show the
least axiality (largest E/D), the iodide salt should show the
largest magnitude of D for the halides, and the perchlorate salt
should show the largest |D| value within the family. As
expected, all computed values suggest minimal rhombic
anisotropy. We attribute this to the placement of the second
anion, which promotes 3-fold rotational symmetry, which in
turn minimizes E. For this reason, we will focus on the axial
component D in the remaining discussion.
Figure 5. Variable frequency out-of-phase ac susceptibility for 1, collected at a
2500 Oe applied dc field in the temperature range 1.8 to 4.6 K. Data were
collected at 0.1 K increments from 1.8 K to 3.4 K and at 0.2 K increments from
3.6 to 4.6 K.
The exhibition of field-induced slow magnetic relaxation
for 1 is concurrent with it being the most axially anisotropic of
the four salts and possessing the largest magnitude axial
anisotropy. Because the halide salts are isostructural,
intermolecular interactions are unlikely to be the source of this
distinction. A caveat is that all three halide-containing salts
show extensive disorder in the one-dimensional channels
formed by packing, including the second charge-balancing
anion, so we cannot completely rule out differences in
CASSCF, NEVPT2, and CASCI give excited state energies
about half of what is computed via TD-DFT47 methods (Table
S9). The more compressed manifold of excited states leads to
larger anisotropy, but the signs of the anisotropy parameters
are opposite and tend to cancel each other out, leading to
small overall anisotropies. This is similar to what Dunbar and
supramolecular
environments
for
the
complexes.
Notwithstanding, we note subtle but significant differences in
local Co(II) geometry owing to the different anions interacting
with the complex. The change in ionic radius going from
4 | J. Name., 2012, 00, 1-3
This journal is © The Royal Society of Chemistry 20xx
Please do not adjust margins

Page 5 of 10
Dalton Transactions
Please do not adjust margins
Journal Name
ARTICLE
coworkers reported for 5-coordinate complexes,9 at least in pronounced effect as R is altered, where at long distances (4.0
View Article Online
terms of competing large anisotropy terms.
Å), the predicted D values are opposiDteOI:in10.1s0ig3n9/,Cb9DuTt0t0h73e9sCe
Whereas the present set of Co(II) complexes display small values nearly converge to a small positive D when R is
positive anisotropies, the recent literature provides many sufficiently short. The more octahedral systems (52.5°, 60°)
examples of Co(II) species with large |D|. As we have shown exhibit a decrease in D as a function of shortening length,
previously for model [Co(NH3)6]2+ model complexes,24 the axial indicating that the role of this parameter is lessened toward
anisotropy parameter for hexacoordinate Co(II) complexes the ends of the trigonal distortion spectrum. For the
tends to either be near -100 or +100 cm-1, depending upon the experimentally observed trigonal distortion and seventh
extent of trigonal distortion.
ammine distance (R) geometric parameters (2.57 Å – 2.71 Å,
These results lead us to computationally investigate the 50˚ - 51˚), the computed D values are small and positive (filled
role of a seventh coordination site on the magnetic anisotropy black circles in Figure 6). These results suggest that the
of these and related species using [Co(NH3)7]2+ as a model. In interaction between the seventh ammine and dσ is responsible
this system, we varied the distance (R) of a seventh ammine for the small positive D observed in complex salts 1-4.
ligand for various trigonal distortion angles. Here, we
As would be expected, the rhombic anisotropy parameter
employed the effective spin Hamiltonian CASSCF/NEVPT2 or E/D is small for octahedral and near trigonal prismatic
CASSCF/CASCI methods41–44,48,49 which has been used structures and maximizes around 38˚ (Figure S24a). There is a
previously by us24,33 and others50–55 for evaluation of magnetic pronounced seventh-ligand distance dependence, the
anisotropy in Co(II) systems. As pointed out previously56 this rhombicity decreasing as the seventh ligand approaches. This
approach is potentially problematic for systems with low-lying is consistent with what is observed experimentally, where 1
excited states. The CASCI results for D are collected in Figure 6. has the smallest rhombicity.
Computed g values are provided as supplementary figures in
The trends in g are as expected, based on literature
the ESI (Figures S24b-d). We note that alternative methods for precedent (Figure S24. For example, for the Co(II) bis-
establishing structural distortion impacts on anisotropy may trispyrazolylborate complex, g∥ is large (8.5) and g⊥ small (1.0),
also be effective but are outside the scope of this paper.57,58
the CASCI computed values are 8.54 and 1.38, respectively. For
the idealized model [Co(NH3)7]2+ complex, g∥ is 9.82 and g⊥
ranges from 0.007 to 0.003 as a function of R. As the structure
distorts toward octahedral g∥ drops to 4.76-4.57. For
intermediate angular distortions there is
seventh-ligand distance dependence.
a pronounced
For intermediate distortions the two smaller components
of g are not degenerate. The intermediate component
smoothly rises with angular distortion while decreasing with
increasing R. The smallest component rises and then
moderates with increasing angular distortion or increasing R.
We note that the guide lines connecting data points in
Figure 6 do not connote a simple distortion pathway by which
the sign and magnitude of D can be switched in the model
complex system. The discontinuities in data for the 30˚ to
45˚degree data likely accrue from limitations the
computational model. The sensitivity of D to geometric
parameters also suggests that two or more states may be
being brought into equilibrium, such that small perturbations
(e.g. changing cation-anion interactions) might push
preference for one state over another. From the model
calculations, the boundary conditions appear to be a seventh
ligand in the range 2.5 Å < R < 3.0 Å, and a trigonal twisting
range of ~20° < φ < 40°. Regarding target structures for
Figure 6. Calculated D values as a function of seventh Co-N distance (R) at given
distortion angles (φ), using face-capped trigonal prismatic [Co(NH3)7]2+ as a
model system. The solid black data points represent the most comparable
trigonal distortion to the complex salts 1-4. Lines serve as guides for the eye.
Previously, Ruiz and co-workers22 predicted that capped
octahedral d7 complexes should yield small positive D values,
while capped trigonal prismatic complexes would yield small
negative D. Here, we find that the sign and magnitude can vary
significantly if the seventh Co-L distance (R) is changed. In our
previous work24, the plus combination of t2g orbitals, labelled
dσ, was found to play a significant role in the sign of D. This
suggests that a seventh ligand oriented along the three-fold
axis would destabilize dσ and could impact D. As can be seen in
Figure 6, when the geometry is more trigonal prismatic in
nature (0°, 15°), there is negligible effect on D even as a
seventh ligand approaches cobalt. On the other hand, systems
with intermediate trigonal twisting (37.5°, 45°) show a
switching behaviour, the tren-based ligands provide
a
coordination environment that is more octahedral than
desired; nevertheless, relatively minor geometric changes, for
example the ~0.05 Å difference between the ester-containing
complex and chloride-bound 1, can combine with other
structural factors to allow a switching event of sorts. We
expect that ligands which drive toward a more trigonal
prismatic geometry will enhance the switching: sharp
sensitivity of D to bond distance shifts of less than 0.1 Å is
predicted.
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 5
Please do not adjust margins

Please do not adjust margins
Dalton Transactions
Page 6 of 10
ARTICLE
Journal Name
ferromagnetic impurities was confirmed by observing the
Conclusions
View Article Online
linearity of a plot of magnetization vs.DfOieI:l1d0.a10t391/0C09DKT.00In739aCll
cases, dc susceptibility measurements were collected from 1.8
K to 300 K under an applied dc field of 1000 Oe. For
magnetization experiments, crystals of 1, 2, and 4 were
encased in six drops of solidified eicosane and crystals of 3
were pressed in a polypropylene powder holder and measured
from 1.8 to 30 K under applied dc fields of 1, 2, 3, 4, and 5 T.
Data were corrected for the magnetization of the sample
holder by subtracting the susceptibility of an empty container
and for diamagnetic contributions of the sample by using
Pascal’s constants.59 Molecular weights used for magnetic
calculations were 1·1.8 CH3OH, 2, 3, 4. Fits of the magnetic
susceptibility data were performed using PHI29 using the
following Hamiltonian:
The results presented herein show in detail how small changes
in the metal coordination environment can drastically
influence dynamic magnetic properties in a Co(II) system. The
flexibility of this tren-based iminopyridine ligand allows for
expansion of the guest binding pocket and association of
anions (even perchlorate). The identity of these anionic guests
affects not only the magnetic anisotropy of the system, but
also the dynamic magnetic properties. This behaviour is most
pronounced in the most contracted system 1, which is the only
salt examined here to show slow magnetic relaxation under
applied external field. Theoretical considerations have also
highlighted the effect of a seventh ligand in a face-capped
hexacoordinate Co(II) environment at varying trigonal
distortions. While either twisting or seventh ligand
compression could promote a magnetic switching event, the
available data and computations suggest that anion binding
affects seventh ligand location more than trigonal twisting. We
are currently developing ligand architectures for host-guest
systems that exploit this distortion pathway to perturb spin-
state equilibria as well as magnetic anisotropy.
2
2
2
∑
(
)
(
)
]
+
퐻 = 퐷푖
[
푆푧,푖 ― 1/3푆푖 푆푖 + 1 + 퐸푖/퐷푖 푆푥,푖 ― 푆푦,푖
∑
푔푥푥,푖훽푆푥,푖 ∙ 퐵푥 + 푔푦푦,푖훽푆푦,푖 ∙ 퐵푦 + 푔푧푧,푖훽푆푧,푖 ∙ 퐵푧
Fits of the reduced magnetization data were obtained with the
PHI29 and ANISOFIT 2.060 program using a spin Hamiltonian of
the form:
2
퐻 = 퐷푆푧 + 퐸 푆2 + 푆2 + 푔푖푠표훽푆 ∙ 퐵
(
)
푦
푥
Experimental
Alternating-current (ac) susceptibility was measured for 1–4
under a 4 Oe ac driving field at frequencies from 1 to 1488 Hz
at 1.8 K under applied dc field from 0 to 5000 Oe. The variable
temperature ac susceptibility measurements for 1 were
performed in the temperature range of 1.8 to 4.6 K under an
applied dc field of 2500 Oe.
General Considerations
Unless otherwise noted, all manipulations were performed
in a dinitrogen filled MBRAUN Labmaster 130 glovebox. The
synthesis and characterization of L5–ONHtBu has been described
elsewhere, but the synthesis of the aldehyde precursor is
described in greater detail here.16 Acetonitrile (MeCN) and
diethyl ether (Et2O) were sparged with dinitrogen, passed over
molecular sieves, and subjected to three freeze-pump-thaw
cycles prior to use. All other reagents were obtained from
commercial sources and used without further purification
unless otherwise indicated. Qualitative thin layer
chromatography (TLC) analysis was performed on 250 mm
thick, 60 Å, glass backed F254 silica (Silicycle, Quebec City,
Canada); samples were visualized with UV light. Flash
chromatography was performed using Silicycle silica gel (230-
400 mesh).
X-ray Structure Determinations
All single crystals were coated in Paratone–N oil prior to
removal from the glovebox. Data collection was performed by
mounting a single crystal on a Cryoloop under a stream of
dinitrogen. Data sets were collected targeting complete
coverage and fourfold redundancy. Integrations of the raw
data were done using the Apex II software package and
absorption corrections were applied using SADABS.61 The
structures were solved using direct methods and refined
against F2 using SHELXTL 6.14 software package.62 Unless
otherwise noted, thermal parameters for all non-hydrogen
atoms were refined anisotropically. Hydrogen atoms were
added at the ideal positions and refined using a riding model in
which the isotropic displacement parameters were set at 1.2
times those of the attached carbon atom (1.5 times for methyl
carbons).
Magnetic Measurements
Magnetic data for 1, 2 and 4 were collected using a
Quantum Design model MPMS-XL superconducting quantum
interference device (SQUID) magnetometer. Measurements
were collected using crystals of 1, 2, and 4 packed into the top
of gelatin capsules and restrained with the bottom portion of
the capsule. All samples were prepared under a dinitrogen
atmosphere and quickly loaded into the SQUID to minimize air
exposure. Direct current (dc) susceptibility measurements of
crystals of 3 were performed on a Quantum Design model
PPMS Dynacool equipped with a VSM transport system. The
sample was encased in a polypropylene powder holder
prepared under a dinitrogen atmosphere and quickly loaded
into the instrument to minimize air exposure. The absence of
In the structures of compounds 1, 2, and 3, one of the
charge-balancing anions appears to be highly disordered over
several locations within an apparent void space. The addition
of disordered solvent molecules further complicates modeling
of the disordered anion. Several attempts to explicitly model
3
the disorder in P did not afford significant improvement to
the agreement factors. Additional attempts to model the
1
disorder in the lower symmetry space group P gave similar
problems with the disordered anion and solvent. Thus,
6 | J. Name., 2012, 00, 1-3
This journal is © The Royal Society of Chemistry 20xx
Please do not adjust margins

Page 7 of 10
Dalton Transactions
Please do not adjust margins
Journal Name
SQUEEZE was employed to remove the residual electron
ARTICLE
[CoL5-ONHtBu]Br2 (2). To a solution of L5–ONHtBu (V4ie3wmArgtic,le0O.0nl6in0e
density due to the second charge balancing anion. The residual mmol) in MeOH (3 mL) was added CoBr2DO(1I:210m.1g0,390/.C095D4T0m0m73o9Cl)
electron density per unit cell for 1 was determined to be 70 in MeOH (3 mL) and the resulting orange mixture was stirred
electrons and 640 Å3, which would account for two chloride at 23 °C for 16 hours. The reaction volume was then
anions and 2 methanol molecules per unit cell. For complex 2, concentrated in vacuo to ~3 mL and diffraction quality crystals
the void space within the crystal lattice was determined to be were grown by ether diffusion into this methanolic solution.
650 Å3 and 114 electrons per unit cell. This equates to two The crystals were isolated by filtration and washed with diethyl
bromide anions and 2.33 methanol (or molecules per unit cell. ether (2 × 5 mL) to give 2 (45 mg, 90% yield). MS (ESI+): m/z
Lastly, the void space of complex 3 was determined to be 675 found: 384.8 ([CoL5–ONHtBu])2+, 848.3 ([CoL5–ONHtBu]Br)+. H NMR
1
Å3 and 284 electrons per unit cell. This equates to two iodide (400 MHz, CD3CN): δ 181, 136, 109, 53, 43, 13, –0.6, –0.8, –15.
anions and 4.2 diethyl ether molecules per unit cell. UV-Vis (CH3CN) λmax/nm (εM/M–1·cm–1) 220 (sh, 45600), 240
Considering the crystalized solvents are diethyl ether the (sh, 35000), 287 (24600), 369 (2900) 450 (sh, 675), 510 (sh,
residual electron density corresponds to 0.85, 1.04 and 4.24 250), 902 (10). Anal Calc’d for C40H61.5Br2CoN10O5.75 (2·1
diethyl ether molecules per unit cell of 1, 2 and 3. As in the CH3OH·1.75 H2O – these solvents were observed in the 1H
NMR we detected presence of methanol we are more inclined NMR spectrum): C, 48.36; H, 6.19; N, 14.11. Found: C, 48.37; H,
to the presence of methanol as the cocrystallized solvent. The 6.24; N, 14.10.
chemical formulas supplied in Table S1 do not account for the
[CoL5-ONHtBu]I2 (3). To a solution of L5–ONHtBu (54 mg, 0.08
disordered components that were removed via SQUEEZE. Full mmol) in MeOH (3 mL) was added a solution of CoI2 (12 mg,
crystallographic information for 1–4 has been deposited with 0.08 mmol) in MeOH (10 mL) and the resulting orange mixture
the CCDC under registry numbers 1030387–1030390.
was stirred at 23 °C for 1 hour. The reaction volume was then
concentrated to ~ 3 mL in vacuo and diffraction quality crystals
were grown by ether diffusion into this methanolic solution.
Other Physical Methods
Infrared spectra were measured with a Nicolet 380 FT–IR The crystals were isolated by vacuum filtration and washed
under a dinitrogen flow using an ATR attachment with a ZnSe with diethyl ether (2 × 5 mL) to give 3 (73 mg, 94% yield). MS
crystal. Visible absorption spectra were obtained using an (ESI+): m/z found: 384.8 ([CoL5–ONHtBu])2+ 769.5 ([CoL5–ONHtBu]-
,
1
Agilent 8453 UV-visible spectrometer under air-free conditions H)+, 896.3 ([CoL5–ONHtBu]I)+. H NMR (400 MHz, CD3CN): δ 178,
1
using a quartz cuvette. H NMR spectra were recorded using 148, 108, 52, 44, 13, 2.3, 0.0, –13. UV-Vis (CH3CN) λmax/nm
Varian INOVA instruments operating at 400 MHz. (εM/M–1·cm–1) 287 (35500), 370 (4000), 450 (sh, 900), 510 (sh,
Paramagnetic spectra were acquired at room temperature 360) 908 (10). Anal Calc’d for C40H59I2CoN10O4.5 (3·1 CH3OH·0.5
collecting 512 scans in a spectral window from -22.5 to 200 H2O – methanol and water are observed in the 1H NMR
ppm using an acquisition time of 1 second and a 1 ms spectrum): C, 45.12; H, 5.59; N, 13.16. Found: C, 44.89; H, 5.44;
relaxation delay. Mass spectra were obtained on a Finnigan N 13.24.
LCQ Duo mass spectrometer equipped with an electrospray
[CoL5-ONHtBu](ClO4)2 (4). To a solution of L5–ONHtBu (150 mg,
ion source and quadrupole ion trap mass analyzer in positive 0.21 mmol) in MeOH (10 mL) was added a solution of
ion mode. Elemental analysis was performed by Robertson Co(ClO4)2·6H2O (81 mg, 0.22 mmol) in MeOH (5 mL) and the
Microlit Laboratories in Ledgewood, NJ.
resulting orange mixture was stirred at 23 °C for 16 hours. The
reaction volume was then concentrated to ~ 3 mL in vacuo and
diffraction quality crystals were grown by ether diffusion into
Synthesis of Co complex salts
Caution! Perchlorate salts are potentially explosive and should this methanolic solution. The crystals were isolated by vacuum
be handled with care and in small quantities! filtration and washed with diethyl ether (2 × 5 mL) to give 4
[CoL5-ONHtBu]Cl2 (1). To a suspension of CoCl2 (18 mg, 0.14 (204 mg, 90% yield). MS (ESI+): m/z found: 384.8 ([CoL5–-
mmol) in MeOH (4.5 mL) was added L5–ONHtBu (96 mg, 0.14 ONHtBu])2+, 868.4 ([CoL5–ONHtBu](ClO4))+. 1H NMR (400 MHz,
mmol) in MeOH (4.5 mL). The resulting orange mixture was CD3CN): δ 177, 160, 108, 51, 44, 13, 4, 0.2, 12. UV-Vis (CH3CN)
stirred at 23 °C for 16 hours to ensure full dissolution of CoCl2. λmax/nm (εM/M–1·cm–1) 237 (31000), 287 (25400), 373 (3200),
The solution was then concentrated to a volume of 2 mL in 450 (sh, 750), 510, (sh, 260), 900 (10). Anal Calcd for
vacuo and diffraction quality crystals were grown by ether C39H54Cl2CoN10O11: C, 48.35; H, 5.62; N, 14.46. Found: C, 48.49;
diffusion into this concentrated methanolic solution. The H, 5.78; 14.46.
crystals were isolated by filtration and washed with diethyl
Synthesis of aldehyde 9 (from which L5-ONHtBu is derived)
ether (2 × 5 mL) to give 1 (96 mg, 85% yield). MS (ESI+): m/z
found: 384.9 ([CoL5–ONHtBu])2+, 768.4 ([CoL5–ONHtBu–H])+, 804.3
Monoester 6. To a suspension of 2,5-pyridinedicarboxylic
([CoL5–ONHtBu]Cl)+. 1H NMR (400 MHz, CD3CN): δ 180, 135, 108, acid (5, 5.68 g, 34.0 mmol) in MeOH (200 mL, 0.17 M) was
53, 43, 13, –1.0, –1.3, –16. UV-Vis (CH3CN) λmax/nm (εM/M– added concentrated aqueous H2SO4 (5.0 mL, 0.0028 mmol)
1·cm–1) 234 (56400), 292, (43100), 373 (2800), 450 (sh, 650), and the resulting mixture was heated to a gentle boil (~70 °C).
510 (sh, 240), 906 (10). Anal Calc’d for C40.8H61.2Cl2CoN10O4.8 When the reaction became transparent, it was poured on ice
(1·1.8 CH3OH – methanol was observed in the 1H NMR and filtered. The precipitate was dissolved in wet THF (100
spectrum): C, 54.54; H, 6.87; N, 15.59. Found: C, 54.35; H, 6.77; mL), dried over MgSO4, filtered and concentrated in vacuo to
15.80.
isolate crude 6. The crude compound was then dried overnight
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 7
Please do not adjust margins

Please do not adjust margins
Dalton Transactions
Page 8 of 10
ARTICLE
Journal Name
in a vacuum oven at 100 °C to give monoester 6 (4.65 g, 75% hexanes/EtOAc eluent) to afford pure 9 (0.730 g,V7ie5w%ArtyicileelOdn,linRef
1
yield) as a pink solid. 1H NMR (400 MHz, CD3OD): δ 9.21 (d, J = = 0.44 in 1:1 hexanes/EtOAc). H NMR (400 MHz, CDCl3): δ
DOI: 10.1039/C9DT00739C
1.6 Hz, 1H), 8.54 (dd, J = 8.0 Hz, 1.6 Hz, 1H), 8.25 (d, J = 8.0 Hz, 10.12 (s, 1H), 9.07 (d, J = 1.2 Hz, 1H), 8.20 (dd, J = 8.0, 1.2 Hz,
1H), 4.01 (s, 3H).
1H), 8.01 (d, J = 8.0 Hz, 1H), 5.96 (br s, 1H), 1.51 (s, 9H).
Scheme 1. Synthesis of aldehyde 9.
Acknowledgments
O
O
O
OH
OH
NHtBu
(a)
(b,c)
This work is supported by NSF (CHE-1363274, CHE-1800554)
and Colorado State University. We thank R. F. Higgins for
assistance with figure preparation.
HO
MeO
MeO
N
N
N
O
O
O
5
6
7
O
O
NHtBu
(d)
(e)
NHtBu
Conflicts of interest
H
HO
N
N
O
There are no conflicts of interest to declare.
8
9
(a) H2SO4 (cat.), MeOH, 70 °C, 75% yield; (b) SOCl2, PhMe, 120 °C; (c) t-BuNH2, Et2O,
0 °C; (d) NaBH4, CaCl2, 2:1 THF:MeOH, 0 to 23 °C, 85% yield (3 steps); (e) SeO2, 1,4-
dioxane, 101 °C, 75% yield
Notes and references
1
H.-H. Cui, J. Wang, X.-T. Chen and Z.-L. Xue, Chem. Commun.,
2017, 53, 9304–9307.
Amide 7. To a suspension of monoester 6 (4.63 g, 25.5
mmol) in anhydrous toluene (80 mL, 0.32 M) was added
dropwise freshly distilled (from quinoline) SOCl2 (5.57 mL, 76.6
mmol) and the resulting mixture heated to reflux (~120 °C).
Upon complete conversion to the acyl chloride (visually
determined as when the reaction turns transparent yellow),
excess SOCl2 and solvent were removed by vacuum distillation
to give the crude acid chloride. This residue was then
redissolved in anhydrous Et2O (160 mL, 0.16 M) and cooled to
0 °C, and tert-butyl amine (10.74 mL, 102.2 mmol) was added
dropwise. The amide formation was immediate as evidenced
by precipitation of the amine hydrochloride salt. The reaction
was allowed to warm to 23 °C and stirred for 1 h. The mixture
was filtered and the precipitate washed with CH2Cl2 (2 × 100
mL). The combined filtrates were concentrated in vacuo to
give crude amide 7 (Rf = 0.61 in EtOAc). This material was used
2
X. Feng, C. Mathonière, I.-R. Jeon, M. Rouzières, A.
Ozarowski, M. L. Aubrey, M. I. Gonzalez, R. Clérac and J. R.
Long, J. Am. Chem. Soc., 2013, 135, 15880–15884.
C. Mathonière, H.-J. Lin, D. Siretanu, R. Clérac and J. M.
Smith, J. Am. Chem. Soc., 2013, 135, 19083–19086.
S. Mossin, B. L. Tran, D. Adhikari, M. Pink, F. W. Heinemann,
J. Sutter, R. K. Szilagyi, K. Meyer and D. J. Mindiola, J. Am.
Chem. Soc., 2012, 134, 13651–13661.
3
4
5
6
L. Chen, J. Song, W. Zhao, G. Yi, Z. Zhou, A. Yuan, Y. Song, Z.
Wang and Z.-W. Ouyang, Dalt. Trans., 2018, 47, 16596–
16602.
F. Habib, J. Long, P.-H. Lin, I. Korobkov, L. Ungur, W.
Wernsdorfer, L. F. Chibotaru and M. Murugesu, Chem. Sci.,
2012, 3, 2158.
S. Zhang, H. Ke, L. Sun, X. Li, Q. Shi, G. Xie, Q. Wei, D. Yang,
W. Wang and S. Chen, Inorg. Chem., 2016, 55, 3865–3871.
Q. Chen, M.-H. Zeng, L.-Q. Wei and M. Kurmoo, Chem.
Mater., 2010, 22, 4328–4334.
T. J. Woods, M. F. Ballesteros-Rivas, S. Gómez-Coca, E. Ruiz
and K. R. Dunbar, J. Am. Chem. Soc., 2016, 138, 16407–
16416.
7
8
9
1
without further purification. H NMR (400 MHz, CDCl3): δ 9.01
(s, 1H), 8.18 (s, 2H), 5.94 (br s, 1H), 4.03 (s, 3H), 1.50 (s, 9H).
Alcohol 8. To a solution of amide 7 (25.5 mmol assumed) in
2:1 MeOH:THF (426 mL, 0.06 M) at 0 °C was added anhydrous
CaCl2 (8.50 g, 76.6 mmol) and NaBH4 (2.90 g, 76.6 mmol), the
10 J. Vallejo, E. Pardo, M. Viciano-Chumillas, I. Castro, P.
Amorós, M. Déniz, C. Ruiz-Pérez, C. Yuste-Vivas, J. Krzystek,
M. Julve, F. Lloret and J. Cano, Chem. Sci., 2017, 8, 3694–
3702.
latter added portionwise so as to control H2 evolution. The 11 X. Zhang, V. Vieru, X. Feng, J.-L. Liu, Z. Zhang, B. Na, W. Shi,
B.-W. Wang, A. K. Powell, L. F. Chibotaru, S. Gao, P. Cheng
and J. R. Long, Angew. Chemie Int. Ed., 2015, 54, 9861–9865.
12 J. Vallejo, F. R. Fortea-Perez, E. Pardo, S. Benmansour, I.
Castro, J. Krzystek, D. Armentano and J. Cano, Chem. Sci.,
2016, 7, 2286–2293.
reaction was allowed to warm to 23 °C and stir overnight.
Upon complete consumption of the starting material (as
indicated by TLC), the reaction was filtered and concentrated
in vacuo to give crude alcohol 8. This residue was purified by
flash column chromatography (CH2Cl2 to 19:1 CH2Cl2/MeOH 13 M. A. Hoselton, L. J. Wilson and R. S. Drago, J. Am. Chem.
Soc., 1975, 97, 1722–1729.
gradient) to give alcohol 8 as a hygroscopic white solid (4.491g,
85% yield over three steps). 1H NMR (400 MHz, CD3OD): δ 8.82
(s, 1H), 8.18 (d, J = 8.0 Hz), 7.62 (d, J = 8.0 Hz, 1H), 4.73 (s, 2H),
1.46 (s, 9H).
Aldehyde 9. To a suspension of alcohol 8 (0.980 g, 4.69
mmol) in 1,4-dioxane (24 mL, 0.20 M) was added SeO2 (0.260
g, 2.34 mmol) and the resulting mixture was heated to a gentle
reflux (~101 °C) overnight. After allowing to cool to 23 °C, the
reaction was filtered through Celite and the filtrate was
14 M. Seredyuk, A. B. Gaspar, V. Ksenofontov, Y.
Galyametdinov, J. Kusz and P. Gütlich, J. Am. Chem. Soc.,
2008, 130, 1431–1439.
15 C. M. Klug, A. M. McDaniel, S. R. Fiedler, K. A. Schulte, B. S.
Newell and M. P. Shores, Dalt. Trans., 2012, 41, 12577.
16 A. M. McDaniel, C. M. Klug and M. P. Shores, Eur. J. Inorg.
Chem., 2013, 943–950.
17 Y. Y. Zhu, C. Cui, Y. Q. Zhang, J. H. Jia, X. Guo, C. Gao, K. Qian,
S. D. Jiang, B. W. Wang, Z. M. Wang and S. Gao, Chem. Sci.,
2013, 4, 1802–1806.
concentrated in vacuo to give crude aldehyde 9. The crude 18 V. V Novikov, A. A. Pavlov, Y. V Nelyubina, M. E. Boulon, O. A.
product was purified by flash column chromatography (1:1
8 | J. Name., 2012, 00, 1-3
This journal is © The Royal Society of Chemistry 20xx
Please do not adjust margins

Page 9 of 10
Dalton Transactions
Please do not adjust margins
Journal Name
ARTICLE
Varzatski, Y. Z. Voloshin and R. E. P. Winpenny, J. Am. Chem. 45 P. G. Szalay, T. Müller, G. Gidofalvi, H. Lischka and R.
View Article Online
DOI: 10.1039/C9DT00739C
Soc., 2015, 137, 9792–9795.
Shepard, Chem. Rev., 2012, 112, 108–181.
19 Y. Y. Zhu, Y. Q. Zhang, T. T. Yin, C. Gao, B. W. Wang and S. 46 A. D. Becke, J. Chem. Phys., 1993, 98, 5648–5652.
Gao, Inorg. Chem., 2015, 54, 5475–5486.
20 J. M. Frost, K. L. M. Harriman and M. Murugesu, Chem. Sci.,
2016, 7, 2470–2491.
47 R. E. Stratmann, G. E. Scuseria and M. J. Frisch, J. Chem.
Phys., 1998, 109, 8218–8224.
48 D. Ganyushin and F. Neese, J. Chem. Phys., 2013, 138,
104113.
21 O. Kahn, Molecular magnetism, VCH, New York, NY, 1993.
22 S. Gomez-Coca, E. Cremades, N. Aliaga-Alcalde and E. Ruiz, J. 49 M. Atanasov, D. Ganyushin, D. A. Pantazis, K. Sivalingam and
Am. Chem. Soc., 2013, 135, 7010–7018.
F. Neese, Inorg. Chem., 2011, 50, 7460–7477.
23 Y. Peng, T. Bodenstein, K. Fink, V. Mereacre, C. E. Anson and 50 R. Herchel, L. Váhovská, I. Potočňák and Z. Trávníček, Inorg.
A. K. Powell, Phys. Chem. Chem. Phys., 2016, 18, 30135–
30143.
24 T. J. Ozumerzifon, I. Bhowmick, W. C. Spaller, A. K. Rappe and
M. P. Shores, Chem. Commun., 2017, 53, 4211–4214.
25 A. M. McDaniel, A. K. Rappé and M. P. Shores, Inorg. Chem.,
2012, 51, 12493–12502.
26 M. Seredyuk, M. C. Munoz, V. Ksenofontov, P. Gutlich, Y.
Galyametdinov and J. A. Real, Inorg. Chem., 2014, 53, 8442–
8454.
27 S. Alvarez, P. Alemany, D. Casanova, J. Cirera, M. Llunell and
D. Avnir, Coord. Chem. Rev., 2005, 249, 1693–1708.
28 D. Casanova, P. Alemany, J. M. Bofill and S. Alvarez, Chem. -
A Eur. J., 2003, 9, 1281–1295.
Chem., 2014, 53, 5896–5898.
51 Y. Z. Zhang, S. Gomez-Coca, A. J. Brown, M. R. Saber, X.
Zhang and K. R. Dunbar, Chem. Sci., 2016, 7, 6519–6527.
52 S. Gómez-Coca, A. Urtizberea, E. Cremades, P. J. Alonso, A.
Camón, E. Ruiz and F. Luis, Nat. Commun., 2014, 5, 4300.
53 D. V. Korchagin, G. V. Shilov, S. M. Aldoshin, R. B. Morgunov,
A. D. Talantsev and E. A. Yureva, Polyhedron, 2015, 102, 147–
151.
54 S. Gómez-Coca, D. Aravena, R. Morales and E. Ruiz, Coord.
Chem. Rev., 2015, 289–290, 379–392.
55 I. Nemec, H. Liu, R. Herchel, X. Q. Zhang and Z. Travnicek,
Synth. Met., 2016, 215, 158–163.
56 C. G. Werncke, E. Suturina, P. C. Bunting, L. Vendier, J. R.
Long, M. Atanasov, F. Neese, S. Sabo-Etienne and S.
Bontemps, Chem. - A Eur. J., 2016, 22, 1668–1674.
29 N. F. Chilton, R. P. Anderson, L. D. Turner, A. Soncini and K. S.
Murray, J. Comput. Chem., 2013, 34, 1164–1175.
30 Y. Ma, A.-L. Cheng and E.-Q. Gao, Dalt. Trans., 2010, 39, 57 M. Pinsky and D. Avnir, Inorg. Chem., 1998, 37, 5575–5582.
3521.
58 L. Gregoli, C. Danieli, A.-L. Barra, P. Neugebauer, G.
Pellegrino, G. Poneti, R. Sessoli and A. Cornia, Chem. - A Eur.
J., 2009, 15, 6456–6467.
31 We do not aim to overstate a magnetostructural correlation
where the anion in the crystal structure differs from the
anion in the magnetic study. Notwithstanding, there are no 59 G. A. Bain and J. F. Berry, J. Chem. Educ., 2008, 85, 532.
obvious hydrogen-bonding donor groups in the ester- 60 M. P. Shores, J. J. Sokol and J. R. Long, J. Am. Chem. Soc.,
containing complex that may distort the structure upon
differential anion-cation interactions, thus it is reasonable to 61 APEX 2, Bruker Analytical X-Ray Systems, Inc.: Madison, WI.,
expect similar local geometries for the two complex salts 2008
32 L. Chen, H.-H. Cui, S. E. Stavretis, S. C. Hunter, Y.-Q. Zhang, 62 G. M. Sheldrick, SHELXTL, Version 6.14; Bruker Analytical X-
2002, 124, 2279–2292.
X.-T. Chen, Y.-C. Sun, Z. Wang, Y. Song, A. A. Podlesnyak, Z.-
W. Ouyang and Z.-L. Xue, Inorg. Chem., 2016, 55, 12603–
12617.
Ray Systems: Madison, WI., 1999
33 R. F. Higgins, B. N. Livesay, T. J. Ozumerzifon, J. P. Joyce, A. K.
Rappé and M. P. Shores, Polyhedron, 2018, 143, 193–200.
34 L. Chen, S.-Y. Chen, Y.-C. Sun, Y.-M. Guo, L. Yu, X.-T. Chen, Z.
Wang, Z. W. Ouyang, Y. Song and Z.-L. Xue, Dalt. Trans.,
2015, 44, 11482–11490.
35 J. Wang, H.-H. Cui, Y.-Q. Zhang, L. Chen and X.-T. Chen,
Polyhedron, 2018, 154, 148–155.
36 B. Drahoš, R. Herchel and Z. Trávníček, Inorg. Chem., 2017,
56, 5076–5088.
37 D. Shao, Y. Zhou, Q. Pi, F.-X. Shen, S.-R. Yang, S.-L. Zhang and
X.-Y. Wang, Dalt. Trans., 2017, 46, 9088–9096.
38 R. Ruamps, L. J. Batchelor, R. Guillot, G. Zakhia, A.-L. Barra,
W. Wernsdorfer, N. Guihery and T. Mallah, Chem. Sci., 2014,
5, 3418–3424.
39 W. H. Harman, T. D. Harris, D. E. Freedman, H. Fong, A.
Chang, J. D. Rinehart, A. Ozarowski, M. T. Sougrati, F.
Grandjean, G. J. Long, J. R. Long and C. J. Chang, J. Am. Chem.
Soc., 2010, 132, 18115–18126.
40 D. E. Freedman, W. H. Harman, T. D. Harris, G. J. Long, C. J.
Chang and J. R. Long, J. Am. Chem. Soc., 2010, 132, 1224–
1225.
41 C. Angeli, S. Borini, M. Cestari and R. Cimiraglia, J. Chem.
Phys., 2004, 121, 4043–4049.
42 C. Angeli, R. Cimiraglia, S. Evangelisti, T. Leininger and J.-P.
Malrieu, J. Chem. Phys., 2001, 114, 10252–10264.
43 C. Angeli, R. Cimiraglia and J.-P. Malrieu, J. Chem. Phys.,
2002, 117, 9138–9153.
44 C. Angeli, R. Cimiraglia and J.-P. Malrieu, Chem. Phys. Lett.,
2001, 350, 297–305.
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 9
Please do not adjust margins

Dalton Transactions
Page 10 of 10
View Article Online
DOI: 10.1039/C9DT00739C
318x112mm (300 x 300 DPI)